#main{
	position:absolute;
	top:0;
	left:0;
	width:100%;
	height:100%;
}
#welcome{
	position:absolute; 
	width:646px; 
	height:446px; 
	text-align:center;
	padding-top:55px;
	left:50%;   
	top:50%;   
	margin-top:-223px;   
	margin-left:-323px;
	background-image:url(../images/bg_welcome.png)
}